Screw propeller



May 8, 1923.

A. GRILLI SCREW PROPELLER Filed Oct. 2'7. 1921 R! m we ma 0 L E m HATTORNEY.

Patented May 8, 1923.

PA ENT OFFICE.

ANGELO GRILLI, OF MILWAUKEE; WISCONSIN.

scanw PROPELLERT Application filed October 27, 1921.. Seria l'No.510,910.

To all whom it may concern:

Be it known thatI, ANGELO GRJLLI, a subject of the King of Italy,residing at Milwaukee, in the county of Milwaukee and 6 State ofWisconsin, have invented a certain new and useful Improvement in ScrewPropellers, of which the following is a full, clear, concise, and exactdescription, reference being had to the accompanying drawin forming apart of this specification.

iis invention relates to screw propellers.

Objectionable vibration is not an uncommon occurrence in the ordinarybladed prollers so commonly used in ship propulsion.

is is due to the limited width of the blades and the consequentuncertain reaction thereof against the water. To avoid this, the

. use of a propeller having extended spiral surfaces has been proposed.The increased surface area thus provided reduces the vibration tendency,but in the propellers of this type heretofore constructed the increasedresistance oifered by the water to this increased area of contactmaterially reduces the efliciency of the propeller.

The general aim of the present invention is the provision of aneflicient, smooth running propeller which will be free of the abovenoted objections. This is accomplished by the use of spiral surfaces ofpregressively increasing width from the forward to the rear of thepropeller.

Other objects and advantages will later ap ar.

85 no embodiment of this invention is illustrated in the accompanyingdrawings, in which:

Figure 1 is an end elevation of a screw propeller constructed inaccordancewith the to present invention.

Figure 2 is a side elevation of the pro peller shown in Figure 1.

Figure 3 is a side elevation of the propeller turned through ,a ninetydegree angle from the position of Figure 2.

The propeller selected for illustration includes a hollow hub 10provided with the usual keyway 11 by which it may be secured to a driveshaft in the usual manner.

so The hub carries a pair of spirals 12 preferably formed as an integralpart thereof and extending substantially from one end of the hub to theother. Each spiral terminates at its opposite ends in narrow straightedges 13 and 14.- radially disposed with respect to the longitudinalaxis of the hub 10. It will be noted from an inspection of Figures 1 and2 that the edges 13 are somewhat shorter than the edges 14, and that theradial width of each spiral surface increases progressively from one end13 toward the other end until a maximum width is obtained at a pointsuch as 15 near the rear end of the spiral. These spirals 12 aresymmetrically arranged with respect to the hub so as to provide a 55well balanced unit, and in the propeller shown each extends through anangle of substantially one hundred and eighty degrees about the axis ofrotation and each is of substantially uniform pitch throughout. It willalso be noted that the pitch of the spirals adjacent the hub portion issubstantially the same as the pitch adjacent the outer edges. In fact,the pitch of the spiral surfaces is substantially the same at alldiameters. In other words, each spiral surface maybe described asgenerated by a line maintained at a substantially constant angle withthe axis of the propeller. In the propeller shown, this generating lineis disposed normal to the axis of the propeller,

as indicated by the normal disposition of the radial edges 13 and 14relative to the propeller axis. This formation of spiral surfacesproduces a driving thrust upon the 35 water in a direction lengthwiserather than radially of the propeller.

In use, the propeller is so mounted that the edges 13 are positioned atthe forward end thereof. As the propeller turns in a counter-clockwisedirection (Fig. 1), both edges cut through the water and the rearsurfaces of the spirals force the water rearwardly and cause an advanceof the propeller. As the propeller advances with re spect to the water,the water is engaged by the surfaces of increasing 'area, with theresult that a progressively increasing gri is established between thepropeller an water. A very good traction is thus afforded. The gradualreduction in the radial width of the spiral surfaces be 0nd the point 15of maximum width pro uces.

a progressively decreasing grip upon the water, thus avoiding an abruptrelease and 106 resulting in a smooth action.

Various changes may be made in the embodiment of the inventionhereinabove described, Without departing from or sacrificing any of theadvantages of the invention as defined in the appended claims.

I claim:

1. A screw propeller having a hub and a pair of symmetrically arrangedspiral surfaces carried thereby, each of said surfaces extending throughsubstantially one hundred and eighty degrees about said hub, and eachgradually increasing in Width from one end to a point in advance of theother end and then decreasing in Width from said point to the other end.

2. A screw propeller having a hub, a pair of spiral surfaces extendingthrough substantially one hundred and eighty degrees about said hub,each surface having a substantially constant pitch at all diameters andhaving a progressively varying Width approaching a maximum between theends thereof.

In Witness whereof, I hereunto subscribe my name this 24th day ofOctober, 1921.

. ANGELO GRILLI.

